Partners' Capital, Mezzanine Equity and Distributions (Distributions) (Details) - USD ($) $ / shares in Units, $ in Thousands	Aug. 14, 2018	May 15, 2018	Feb. 14, 2018	Nov. 14, 2017	Aug. 14, 2017	May 15, 2017
Partners Capital And Distributions [Line Items]
Date Paid		May 15, 2018	Feb. 14, 2018	Nov. 14, 2017	Aug. 14, 2017	May 15, 2017
Per Unit Amount (in dollars per unit)		$ 0.5200	$ 0.5100	$ 0.5000	$ 0.7225	$ 0.7200
Total Amount		$ 63,741	$ 62,515	$ 61,290	$ 88,563	$ 88,257
Subsequent Event | Scenario, Forecast
Partners Capital And Distributions [Line Items]
Date Paid	Aug. 14, 2018
Per Unit Amount (in dollars per unit)	$ 0.5300
Total Amount	$ 64,967